The present invention relates to a prefetching queue control system for controlling a buffer or a prefetching queue for storing prefetched instructions in a computer in which, in parallel to the execution of one instruction, a subsequent instruction is stored in the buffer prior to the execution thereof, i.e., so-called prefetching is performed.
Recently, computers increasingly are using a prefetching function in order to increase their processing speed. For purposes of easier control, most of the conventional computers using a prefetching function are being controlled so that when branching occurs because of a branch instruction or an interruption, a prefetching queue is temporarily emptied, i.e., prefetched instructions are rendered invalid. Therefore, the execution of an instruction by a computer is stopped until an instruction at a branch destination is read out and is stored in the prefetching queue.
As described above, in conventional computers, vacant time in which execution of an instruction is temporarily stopped is caused when branching occurs. Since the frequency of occurrence of branching is high in most programs, the total vacant time is inevitably increased.